A spliff that has not been tapped down enough after rolling, so that when it is held by the roach the rest of the spliff droops down, giving the appearance of having been been cut off and sewn back on again.

Named, of course, after the (in)famous John Wayne Bobbitt.

Bobbitting is especially common when backrolling, as the single layer of paper lacks rigidity.

Aw man, I just bobbitted the spliff I was rolling.

Don't backroll the spliff - you always roll bobbitts when you do that.